The present invention concerns a measuring device for measuring both the depth of a hole and the length of a fixing for such a hole. More particularly, but not exclusively, this invention concerns a device for measuring both the depth of a hole in a composite material aircraft component and for measuring the length of a fixing for insertion into such a hole.
When fixing elements together with a bolt or other fixing that passes through a bore through the elements, particularly when the elements are made of differing materials, it is common to provide a sleeve, for example in the form of a bushing or a bearing arrangement, to line the bore within one or more of the elements. One method of securing the sleeve within the bore is to insert the sleeve in the bore and then cold expand the sleeve within the bore. Such a technique is utilised in the GromEx™ system provided by “FTI” (Fatigue Technology, Inc of Seattle, USA). Briefly, a sleeve received in a bore in a part is expanded by means of a hydraulic puller unit (for example the “Big Brute” Puller—Part No. 2720-008, also from FTI), which exerts a pulling force that pulls a mandrel through the sleeve, whilst the puller unit reacts at least some of the pulling force by means of a nose cap of the unit that butts against the surface of the part that defines the bore. A bolt may then be accommodated within the sleeve to fix the part to another element or part. In some cases, the bolt may form a friction fit or an interference fit with the sleeve.
It is important when installing such a GromEx™ sleeve, for the correct length of sleeve to be installed in the hole. Thus, it is necessary to measure the depth of the hole and then find a sleeve of the correct length for use with the hole. The depth of the hole and the length of the sleeve for insertion in the hole should ideally be manually checked immediately before the sleeve is installed in the hole. If an incorrectly sized sleeve is fitted, the structural integrity of the structure immediately surrounding the sleeve and/or of the sleeve and/or of the bolt in the sleeve may be prejudiced. The bolt to be inserted in the sleeve may also need to be chosen and/or checked so as to of a correct length.
There is therefore a need for one or more tools for measuring such dimensions: one or more of the hole depth, the sleeve length, and the bolt length. The engineers who work on aircraft components are prone to losing such tools. Tools used to measure lengths or depths in the aircraft industry are typically made of metal so as to be rigid, and therefore maintain their accuracy (not flex or bend in use so as to deform to a non-linear shape when supposed to be measuring a linear distance), and hard-wearing to withstand the harsh assembly-line/manufacturing/maintenance environment in which they are typically used.
The present invention seeks to mitigate the above-mentioned problem(s). Alternatively or additionally, the present invention seeks to provide an improved means for measuring hole depth and/or the length of a fixing for use in such a hole.